[INET]: Remove per bucket rwlock in tcp/dccp ehash table.
As done two years ago on IP route cache table (commit
22c047ccbc68fa8f3fa57f0e8f906479a062c426) , we can avoid using one
lock per hash bucket for the huge TCP/DCCP hash tables.
On a typical x86_64 platform, this saves about 2MB or 4MB of ram, for
litle performance differences. (we hit a different cache line for the
rwlock, but then the bucket cache line have a better sharing factor
among cpus, since we dirty it less often). For netstat or ss commands
that want a full scan of hash table, we perform fewer memory accesses.
Using a 'small' table of hashed rwlocks should be more than enough to
provide correct SMP concurrency between different buckets, without
using too much memory. Sizing of this table depends on
num_possible_cpus() and various CONFIG settings.
This patch provides some locking abstraction that may ease a future
work using a different model for TCP/DCCP table.
Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Acked-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/inet6_hashtables.c b/net/ipv6/inet6_hashtables.c
index d6f1026..adc73ad 100644
--- a/net/ipv6/inet6_hashtables.c
+++ b/net/ipv6/inet6_hashtables.c
@@ -37,9 +37,8 @@
} else {
unsigned int hash;
sk->sk_hash = hash = inet6_sk_ehashfn(sk);
- hash &= (hashinfo->ehash_size - 1);
- list = &hashinfo->ehash[hash].chain;
- lock = &hashinfo->ehash[hash].lock;
+ list = &inet_ehash_bucket(hashinfo, hash)->chain;
+ lock = inet_ehash_lockp(hashinfo, hash);
write_lock(lock);
}
@@ -70,9 +69,10 @@
*/
unsigned int hash = inet6_ehashfn(daddr, hnum, saddr, sport);
struct inet_ehash_bucket *head = inet_ehash_bucket(hashinfo, hash);
+ rwlock_t *lock = inet_ehash_lockp(hashinfo, hash);
prefetch(head->chain.first);
- read_lock(&head->lock);
+ read_lock(lock);
sk_for_each(sk, node, &head->chain) {
/* For IPV6 do the cheaper port and family tests first. */
if (INET6_MATCH(sk, hash, saddr, daddr, ports, dif))
@@ -92,12 +92,12 @@
goto hit;
}
}
- read_unlock(&head->lock);
+ read_unlock(lock);
return NULL;
hit:
sock_hold(sk);
- read_unlock(&head->lock);
+ read_unlock(lock);
return sk;
}
EXPORT_SYMBOL(__inet6_lookup_established);
@@ -175,12 +175,13 @@
const unsigned int hash = inet6_ehashfn(daddr, lport, saddr,
inet->dport);
struct inet_ehash_bucket *head = inet_ehash_bucket(hinfo, hash);
+ rwlock_t *lock = inet_ehash_lockp(hinfo, hash);
struct sock *sk2;
const struct hlist_node *node;
struct inet_timewait_sock *tw;
prefetch(head->chain.first);
- write_lock(&head->lock);
+ write_lock(lock);
/* Check TIME-WAIT sockets first. */
sk_for_each(sk2, node, &head->twchain) {
@@ -216,7 +217,7 @@
__sk_add_node(sk, &head->chain);
sk->sk_hash = hash;
sock_prot_inc_use(sk->sk_prot);
- write_unlock(&head->lock);
+ write_unlock(lock);
if (twp != NULL) {
*twp = tw;
@@ -231,7 +232,7 @@
return 0;
not_unique:
- write_unlock(&head->lock);
+ write_unlock(lock);
return -EADDRNOTAVAIL;
}